In this laboratory study, the role of juvenile hormone (JH) and ecdysone in regulating wing polyphenism was investigated in the non-model organism Gerris buenoi. Topical application of the JH analog methoprene elicited reduced pronotum, wing defects, and nymphal-adult intermediates but no changes to wing morph. Similarly, while microinjection of the ecdysone derivative 20-hydroxyecdysone (20E) elicited aberrant phenotypes there was again no influence on the wing morph. Using data from a transcriptomics experiment, RNAi knockdown of the differentially expressed 20E induced receptor gene, Hr4, caused high mortality rates (> 90 %) which resulted in a sample size too small to draw any inferences of Hr4’s involvement in G. buenoi wing polyphenism. My results indicate that both JH and ecdysone are involved in several developmental processes including wing development, but they do not seem to be important for determining wing polyphenism. However, several factors are important to consider in future research which means that the potential role of JH and ecdysone in G. buenoi wing polyphenism should not be dismissed at this stage.

Wing polyphenism in insects is a type of phenotypic plasticity where environmental factors trigger the development of a set of discrete wing morphologies. In the water strider Gerris buenoi, photoperiods are the main environmental cue that trigger wing morph determination. The genetic mechanisms connecting environmental cues and the determination of wing morph in G. buenoi are not clear. However, recent experimental work suggests that engagement of the Hippo pathway via ecdysone signalling is a promising model for further investigation. In this study, a reverse-transcription quantitative PCR (RT-qPCR) protocol was developed, aimed at elucidating this potential transduction pathway by quantifying gene expression of Fat, Dachsous, Yorkie, EcR, E75 and E74. This was done using melt curve analysis, gel electrophoresis, sequencing of RT-qPCR products and qPCR standard curves. Additionally, wing morph distribution in extreme and intermediate photoperiods were examined. Wing morph proportions were significantly different between adults emerging in the intermediate photoperiods 15.30:8.30 and 15:9 (hours light : hours dark). An effect of sex was observed, with a higher probability of males becoming long-winged compared to females. This has likely evolved as a result of a dispersal-reproduction trade-off. Taken together, this study provided insight for future investigations of periodically induced wing morph determination and its genetic mechanisms in G. buenoi that will contribute to the understanding of phenotypic plasticity.